β, β-dihydroxy meso-substituted chlorins, isobacteriochlorins, and bacteriochlorins

ABSTRACT

A β,β&#39;-dihydroxy meso-substituted chlorin, bacteriochlorin or isobacteriochlorin compound having the formula (I) or (II): ##STR1## wherein M is a metal. A novel method for synthesizing the compound of formula (I) or (II) comprises the steps of: 
     a. osmylating a β.β&#39;-unsubstituted, meso-substituted porphyrin to form an osmate ester at the β,β&#39;-position, and 
     b. reducing the osmate ester to form the corresponding β,β&#39;-dihydroxy meso-substituted chlorin, bacteriochlorin or isobacteriochlorin of formula (I) or (II).

FIELD OF THE INVENTION

The present invention relates to certain dihydroxy chlorin,bacteriochlorin or isobacteriochlorin compounds and their preparation.In particular, the invention relates to the dihydroxylation ofβ,β'-unsubstituted tetrapyrrolic macrocycles that have been substitutedin some or all four meso-positions with an alkyl group or an aromaticring. Many of these compounds are useful photosensitizers in the fieldof photodynamic therapy ("PDT") for mediating the destruction ofunwanted cells or tissues or other undesirable materials by irradiation.

BACKGROUND ART

In the field of PDT, various tetrapyrrolic macrocycles, such aspurpurins, chlorins, bacteriochlorins, phthalocyanines and benzochlorinshave shown the ability both to localize at a tumor site and to absorblight to form an activated state in response to the light. Thesemacrocycles then exhibit a cytotoxic effect on the cells or othertissues in which they are localized when irradiated at the appropriatewavelength.

To cause the desired phototoxic effect deep within a subject's tissue,however, it is necessary to use photosensitizers that possess highabsorption coefficients at wavelengths longer than 650 nm, where bodytissues are most transparent to light. See Sternberg et al., "AnOverview of Second Generation Drugs for Photodynamic Therapy IncludingBPD-MA (Benzoporphyrin Derivative)", Photodynamic Therapy and BiomedicalLasers, 470-4 (Spinelli et al. eds. 1992).

The reduction of a porphyrin to form a chlorin (i.e., adihydroporphyrin) changes the optical properties in this desirable way,and reducing the chlorin further to form a bacteriochlorin (i.e., atetrahydroporphyrin) makes the desired effect even more pronounced.There has only been one general method known to convert meso-tetraphenylporphyrins into the corresponding chlorins, namely the diimide reductionintroduced by Whitlock et al., "Diimide Reduction of Porphyrins", J. Am.Chem. Soc., 91, 7485-89 (1969). However, the product produced does nothave a β,β'-dihydroxy substitution pattern.

In addition to the desirable absorptive properties of chlorins andbacteriochlorins, the amphiphilic character of these compounds has beenpointed out as being potentially beneficial with respect to the desiredbiodistribution of the drug. For example, Bonnett et al., "SecondGeneration Tumour Photosensitisers: The Synthesis and BiologicalActivity of Octaalkyl Chlorins and Bacteriochlorins with GradedAmphiphilic Character", J. Chem. Soc., Perkin Trans. 1, 1465-70 (1992),have suggested that meso-tetra(hydroxyphenyl)chlorins and theircorresponding bacteriochlorins could be used as photosensitizers in PDT.

It is known that β-substituted porphyrins can be treated with osmiumtetroxide (OsO₄) to oxidize one or more double bonds, thus forming anosmate ester at the β,β'-position, which can then be reduced with anyone of a variety of reducing agents to form the correspondingvicinal-diol. For example, in Chang et al., "A Novel Method ofFunctionalizing the Ethyl Chain of Octaethylporphyrin", J. Org. Chem.,52, 926-29, the corresponding diol was obtained by oxidizingoctaethylporphyrin with OsO₄ in the presence of pyridine. ##STR2##Osmylation of a completely β,β'-alkyl substituted,5,15-bis-(methylphenyl)porphyrin has similarly produced thecorresponding diol. Osuka et al., "Synthesis of 5,15-Diaryl-SubstitutedOxochlorins from 5,15-Diaryl-octaethylporphyrin", Bull. Chem. Soc. Jap.,66, 3837-39 (1993).

However, the diols so produced tend to undergo a pinacol-pinacolone-typerearrangement when exposed to acidic conditions, yielding oxochlorins,as shown below: ##STR3## When the migratory aptitude of varioussubstituents was studied, it was established that, from therearrangement of the β-monoalkyl-substituted diols, hydrogen was the"substituent" with the greatest tendency to migrate in a rearrangementreaction. Chang et al., "Migratory Aptitudes in Pinacol Rearrangement ofvic-Dihydroxychlorins", J. Heterocyclic Chem., 22, 1739-41 (1985).

Vicinal-dihydroxychlorins have been obtained from β,β'-alkyl substitutedporphyrins by oxidation with osmium tetroxide in pyridine, and it hasbeen confirmed that the product undergoes a pinacol rearrangement ontreatment with sulfuric acid. See Bonnett et al., "The Oxidation ofPorphyrins with Hydrogen Peroxide in Sulphuric Acid", Proc. Chem. Soc.,371-72 (1964), and Chang et al., "Differentiation of Bacteriochlorin andIsobacteriochlorin Formation by Metallation. High Yield Synthesis ofPorphyrindiones via OsO₄ Oxidation", J. Chem. Soc., Chem. Commun.,1213-15 (1986). However, it has not been thought that the dihydroxyosmylation product of a β,β'-unsubstituted, meso-substituted porphyrinwould be stable in view of the likelihood of rearrangement.

Further, if the starting porphyrin bears a β-substitution pattern, whichlowers the overall symmetry of the molecule, dihydroxylation leads to anon-statistical mixture of stereo- and regioisomers. For example, whenthe dimethyl ester of deuteroporphyrin-IX is osmylated, a mixture of thefollowing regioisomers and their corresponding stereoisomers isproduced. Chang et al., "C-Hydroxy- and C-Methylchlorins. A ConvenientRoute to Heme d and Bonellin Model Compounds", J. Org. Chem., 50,4989-91 (1985). ##STR4## Under the best of conditions, the separation ofthese regioisomers and stereoisomers is cumbersome.

It has now been found that β,β'-unsubstituted, meso-substitutedporphyrin compounds can be β,β'-dihydroxylated via the addition of OsO₄,followed by reduction to give the vic-diol, as shown below: ##STR5## Theresulting meso-substituted vic-diols are unexpectedly stable.Surprisingly, dehydration and rearrangement only takes place underrelatively harsh conditions, such as treatment with refluxing benzenecontaining catalytic amounts of HClO₄. This is unexpected in view of,not only the high migratory aptitude of the β-hydrogens, but also theexpected tendency of the molecule to eliminate water, thusreconstituting a fully conjugated, porphyrin resonance structure as theenolic tautomer, as shown below. Crossley et al., "Tautomerism in2-Hydroxy-5,10,15,20-tetraphenylporphyrin: An Equilibrium Between Enol,Keto, and Aromatic Hydroxyl Tautomers", J. Org. Chem., 53, 1132-37(1988). ##STR6## Such meso-phenyl oxoporphyrins have been previouslyprepared via a fundamentally different route. See, e.g., Catalano etal., "Efficient Synthesis of 2-Oxy-5,10,15,20-tetraphenylporphyrins froma nitroporphyrin by a Novel Multi-Step Cine-substitution Sequence", J.Chem. Soc., Chem. Comm., 1537-38 (1984).

It has been found that, when hydroxy groups are added to a pre-existingmeso-substituent, for example, the phenyl substituents inmeso-tetra(hydroxyphenyl)-porphyrins, chlorins and bacteriochlorins canbe effective as active PDT agents. See Berenbaum et al.,"Meso-Tetra(hydroxyphenyl)-porphyrins, a New Class of Potent TumourPhotosensitisers with Favourable Selectivity," Br. J. Cancer, 54, 717-25(1986) and Ris et al., "Photodynamic Therapy withm-Tetrahydroxyphenylchlorin in vivo: Optimization of the TherapeuticIndex", Int. J. Cancer, 55, 245-49 (1993). By introducinghydroxy-functionalities into the β-positions, not only has a new classof photosensitizer compounds been found, but there is reason to believethat the photosensitizers of the invention are even superior to knowncompounds due to enhancement of amphiphilicity of the molecule.

Further, upon β,β'-dihydroxylation, the high symmetry of the startingmaterials causes the formation of only one regio- and stereoisomer ofthe resulting chlorin. For example, the dihydroxylation ofmeso-tetraphenylporphyrin generates only one isomer ofβ,β'-dihydroxy-meso-tetraphenylbacteriochlorin. Further still,subsequent β,β'-dihydroxylation of the β,β'-hydroxychlorin generatesonly two, easily separable diastereomers of thetetrahydroxybacteriochlorin product. This significant reduction ofisomers provides a method for obtaining PDT agents in high yields, whichis of great practical, economical and medicinal importance.

Consistent with previous observations (see, e.g., Whitlock et al ,"Diimide Reduction of Porphyrins" J. Am. Chem. Soc., 91, 7485-89 (1969)and Chang et al. "Differentiation of Bacteriochlorin andIsobacteriochlorin Formation by Metallation: High Yield Synthesis ofPorphyrindiones via OsO₄ Oxidation", J. Chem. Soc., Chem. Comm., 1213-15(1986)), the β-hydroxylation of β,β'-dihydroxychlorins (and the diimidereduction β,β'-dihydroxychlorins or, for that matter, theβ,β'-dihydroxylation of tetraphenylchlorins) are susceptible to apronounced metal-directing effect. Osmylation/reduction ofmetallochlorins produces a metallo-isobacteriochlorin chromophore, fromwhich the parent isobacteriochlorin chromophore can be obtained bydemetallation. In contrast, osmylation/reduction of the free basechlorins produces the corresponding bacteriochlorin chromophores.

Yet another advantage is that the meso-substituent can be widelyderivatized, particularly when it is an aryl ring, such as a phenylgroup. Thus, by hydroxylating β,β'-unsubstituted, meso-substitutedporphyrins and chlorins via oxidation with OsO₄, followed by reductionof the intermediate osmate ester formed at the β,β'-position, there canbe made a number of related vic-diol substituted chlorins andbacteriochlorins exhibiting particularly desirable characteristics asPDT agents, such as intensified and bathochromically shifted Q bands andincreased amphiphilicity. Moreover, due to the ability to furtherderivatize the meso-substituents themselves, an opportunity is providedfor fine-tuning the pharmacokinetics and -dynamics of the compounds toan even greater degree.

DISCLOSURE OF THE INVENTION

According to the present invention, there have been prepared novelβ,β'-dihydroxy meso-substituted chlorin, isobacteriochlorin andbacteriochlorin compounds having the formula (I) or (II): ##STR7##wherein M is a metal selected from the group consisting of Ni(II),Cu(II), Zn(II), Fe(III)Cl, Sn, Ge, Si, Ga, Al, Mn(III), Gd(III), In andTc;

A is a ring having the structure: ##STR8##

D is a ring having the structure: ##STR9## R₁ through R₆ areindependently a hydrogen atom, a lower alkyl group, a lower alkylcarboxylic acid or acid ester group, keto, hydroxy, nitro, amino or agroup that, taken together with another ring, ring substituent ormeso-substituent, forms a fused 5- or 6-membered ring; and

S¹ through S⁴ are H, substituted or unsubstituted alkyl groups, orsubstituted or unsubstituted aromatic rings, which may be the same ordifferent, with the proviso that at least one of S¹ through S⁴ is not H.

Further, a method has been found for efficiently synthesizing thecompounds of formulas (I) and (II). Specifically, in the invention, amethod for making a compound having formula (I) comprises the steps of:

a. osmylating a meso-substituted metalloporphyrin having the formula(III): ##STR10## where A, D, R₁ through R₆ and S¹ through S⁴ aredescribed above, to form an osmate ester at the β,β'-position; and

b. reducing the osmate ester to form the corresponding β,β'-dihydroxymeso-substituted chlorin, bacteriochlorin or isobacteriochlorin offormula (I).

Three methods of making the demetallated compounds of formula (II) aredisclosed. The first comprises the steps of:

a. osmylating a meso-substituted metalloporphyrin having the formula(III) to form an osmate ester at the β,β'-position;

b. reducing the osmate ester to form the corresponding β,β'-dihydroxymeso-substituted chlorin, bacteriochlorin or isobacteriochlorin offormula (I); and

c. demetallating the β,β'-dihydroxy meso-substituted chlorin,bacteriochlorin or isobacteriochlorin of formula (I) after the reducingstep to form the demetallated β,β'-dihydroxy meso-substituted chlorin,bacteriochlorin or isobacteriochlorin of formula (II).

The second method of making a demetallated compound of formula (II)comprises the steps of:

a. osmylating a meso-substituted metalloporphyrin having the formula(III) to form an osmate ester at the β,β'-position; and

b. demetallating the osmate ester; and

c. reducing the demetallated osmate ester to form the correspondingβ,β'-dihydroxy meso-substituted chlorin or bacteriochlorin compound offormula (II).

Yet a third method of making a demetallated compound of formula (II)comprises the steps of:

a. osmylating a meso-substituted porphyrinogenic compound having theformula (IV) ##STR11## where A, D, R₁ through R₆ S¹ through S⁴ are asdescribed above, to form an osmate ester at the β,β'-position; and

b. reducing the osmate ester to form the corresponding β,β'-dihydroxymeso-substituted chlorin or bacteriochlorin compound of formula (II).

BRIEF DESCRIPTION OF DRAWINGS

The present invention will be more clearly understood by referring tothe following drawings, in which:

FIG. 1 shows the UV-Vis spectrum of 2,3-vic-dihydroxy-tetraphenylchlorin(solid line) and the UV-Vis spectrum of[2,3-vic-dihydroxy-tetraphenylchlorinato] zinc (II) (broken line).

FIG. 2 shows the UV-Vis spectrum of2,3-vic-dihydroxy-tetraphenylbacteriochlorin.

FIG. 3 shows the UV-Vis spectrum of2,3,12,13-tetrahydroxy-tetraphenylbacteriochlorin-E-isomer (solid line)and the UV-Vis spectrum of2,3,12,13-tetrahydroxy-tetraphenylbacteriochlorin-Z-isomer (brokenline).

FIG. 4 shows the UV-Vis spectrum of[7,8-vic-dihydroxy-tetraphenylisobacteriochlorinato]zinc(II).

FIG. 5 shows the UV-Vis spectrum of2,3,7,8-tetrahydroxy-tetraphenylisobacteriochlorin-E-isomer (solid line)and[2,3,7,8-tetrahydroxy-tetraphenylisobacteriochlorinato]zinc(II)-E-isomer(broken line).

MODES OF CARRYING OUT THE INVENTION

The β,β'-dihydroxy meso-substituted chlorin, bacteriochlorin orisobacteriochlorin compounds of the invention have formula (I) orformula (II), as described and shown above. M in formula (I) can be anymetal species that is capable of forming the complex of formula (I), butis preferably selected from the group consisting of Ni(II), Cu(II), Zn,Sn, Ge, Si, Ga and Al. An important characteristic of the metal selectedis that it should be possible to introduce the metal into the porphyrinstructure and then also possible to remove it from the chlorin resultingfrom the process of the invention.

A can be any ring having the structure: ##STR12##

D can be any ring having the structure: ##STR13## It should beunderstood that all corresponding resonance forms of the abovestructures are also intended to be covered by the terms "A" and "D".Preferably, however, at least one of the rings A and D is identical tothe rings B and C. Even more preferably, both rings A and D areidentical to the other rings B and C and, with them, form a porphyrincore structure having four such rings, each ring being connected by abridging carbon atom that is referred to as the meso-position.

R₁ through R₆ can be any one of a large number of ring substituents, solong as they do not interfere with the osmylation and reduction stepsoutlined above. Preferably, R₁ through R₆ are independently a hydrogenatom; a lower alkyl group, such as methyl, ethyl, n-propyl, isopropyl,t-butyl and n-pentyl; a lower alkyl carboxylic acid, such as formyl,carboxymethyl, carboxyethyl, carboxy-n-butyl, carboxy-sec-butyl,carboxy-n-hexyl; a carboxylic acid ester group, such as --CH₂ CH₂COOCH₃, --CH₂ CH₂ COOCH₂ CH₃, --CH₂ CH(CH₃)COOCH₂ CH₃, --CH₂ CH₂ CH₂COOCH₂ CH₂ CH₃, --CH₂ CH(CH₃)₂ COOCH₂ CH₃ ; keto; hydroxy; nitro; amino;or the like.

Further, R₁ and R₂, R₃ and R₄, or R₅ and R₆, can be taken together withanother ring, ring substituent or meso-substituent to form a fused 5- or6-membered ring. The fused 5- or 6-membered ring so formed may be anysaturated or unsaturated, carbocyclic or heterocyclic 5- or 6-memberedring that does not interfere with the osmylation and reduction reactionsteps of the invention. Examples of such rings include cyclopentane,furan, thiophene, pyrrole, isopyrrole, 3-isopyrrole pyrazole,2-isoimidazole, 1,2,3-triazole, 1,2,4-triazole, 1,2-dithiole,1,3-dithiole, 1,2,3-oxathiole, isoxazole, oxazole, thiazole,isothiazole, 1,2,3-oxadiathiazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole,1,3,4-oxadiazole, 1,2,3-dioxazole, 1,2,4-dioxazole, 1,2,5-oxathiazole,1,3-oxathiole, benzene, cyclohexane, 1,2-pyran, 1,4-pyran, 1,2-pyrone,1,4-pyrone, 1,2-dioxin, 1,3-dioxin (dihydro form), pyridine, pyridazine,pyrimidine, pyrazine, piperazine, 1,3,5-triazine, 1,2,4-triazine,1,2,4-oxazine, 1,3,2-oxazine, o-isoxazine, 1,2,5-oxathiazine,1,4-oxazine, p-isoxazine, 1,2,6-oxathiazine, 1,3,5,2-oxadiazine,morpholine, azepine, oxepin, thiepin, 1,2,4-diazepine, and the like.Preferably, when R₁ and R₂, R₃ and R₄, or R₅ and R₆, form a fused, 5- to6-membered ring, the ring is a 6-membered ring. Most preferably, when R₁and R₂, R₃ and R₄, or R₅ and R₆, form a ring, it is a 6-memberedcarbocyclic ring, i.e., a benzene ring.

In a particularly preferred embodiment, R₁ through R₆ are independentlyhydrogen, methyl, ethyl, or lower alkyl esters, most preferably beinghydrogen, methyl or ethyl.

S¹ through S⁴ are the same or different and can be H, any one of a largenumber of substituted or unsubstituted alkyl groups, substituted orunsubstituted cycloalkyl groups, and aromatic rings. When one or more ofS¹ through S⁴ is an alkyl group, they preferably have from about 1 toabout 18 carbon atoms, more preferably about 1 to 12 carbon atoms and,even more preferably, about 1-6 carbon atoms. Examples of typical alkylgroups are methyl, ethyl, isopropyl, sec-butyl, tert-butyl, n-pentyl andn-octyl.

When one or more of S¹ through S⁴ is an alkyl group, it may beunsubstituted or substituted with any group that does not interfere withthe osmylation or reduction reactions. For example, when one or more ofS¹ through S⁴ is an alkyl group may be substituted by a halogen atom,such as fluorine, chlorine or bromine; a hydroxy group, such as inpentoses and hexoses; thiol; or a carbonyl group, such as when the alkylgroup is an aldehyde, ketone, carboxylic acid (e.g., a fatty acid) orester or amide; a primary, secondary, tertiary, or quaternary aminogroup; nitrile; a phosphate group; a sulfonate group; and the like.

When one or more of S¹ through S⁴ is a cycloalkyl group, it preferablycontains from about 3 to about 7 carbon atoms. Examples of typicalcycloalkyl groups include cyclopropyl, cyclohexyl, and cycloheteroalkyl,such as glucopyranose or fructofuranose sugars. When one or more of S¹through S⁴ is a cycloalkyl group, it may be unsubstituted or substitutedwith any group that does not interfere with the osmylation or reductionreactions. For example, when one or more of S¹ through S⁴ is acycloalkyl group, they may be substituted by any of the samesubstituents described above for the case when one or more of S¹ throughS⁴ is an alkyl group.

When one or more of S¹ through S⁴ is an aryl group, it preferablycontains from about 5 to about 12 carbon atoms, optionally containingone or more heteroatoms, and optionally including rings that are fusedto the existing conjugated porphyrin ring structure. Examples ofsuitable aromatic rings include furan, thiophene, pyrrole, isopyrrole,3-isopyrrole, pyrazole, 2-isoimidazole, 1,2,3-triazole, 1,2,4-triazole,1,2-dithiole, 1,3-dithiole, 1,2,3-oxathiole, isoxazole, oxazole,thiazole, isothiazole, 1,2,3-oxadiazole, 1,2,4-oxadiazole,1,2,5-oxadiazole, 1,3,4-oxadiazole, 1,2,3,4-oxatriazole,1,2,3,5-oxatriazole, 1,2,3-dioxazole, 1,2,4-dioxazole, 1,3,2-dioxazole,1,3,4-dioxazole, 1,2,5-oxathiazole, 1,3-oxathiole, benzene, 1,2-pyran,1,4-pyran, 1,2-pyrone, 1,4-pyrone, 1,2-dioxin, 1,3-dioxin, pyridine,N-alkyl pyridinium, pyridazine, pyrimidine, pyrazine, 1,3,5-triazone,1,2,4-triazine, 1,2,3-triazine, 1,2,4-oxazine, 1,3,2-oxazine,1,3,6-oxazine, 1,4-oxazine, o-isoxazine, p-isoxazine, 1,2,5-oxathiazine,1,4-oxazine, o-isoxazine, p-isoxazine, 1,2,5-oxathiazine,1,2,6-oxathiazine, 1,4,2-oxadiazine, 1,3,5,2-oxadiazine, azepine,oxepin, thiepin, 1,2,4-diazepine, indene, isoindene, benzofuran,isobenzofuran, thionaphthene, isothionaphthene, indole, indolenine,2-isobenzazole, 1,4-pyrindine, pyrando[3,4-b]-pyrrole, isoindazole,indoxazine, benzoxazole, anthranil, naphthalene, 1,2-benzopyran,1,2-benzopyrone, 1,4-benzopyrone, 2,1-benzopyrone, 2,3-benzopyrone,quinoline, isoquinoline, 1,2-benzodiazine, 1,3-benzodianzine,naphthyridine, pyrido[3,4-b]-pyridine, pyrido[3,2-b]-pyridine,pyrido[4,3-b]-pyridine, 1,3,2-benzoxazine, 1,4,2-benzoxazine,2,3,1-benzoxazine, 3,1,4-benzoxazine, 1,2-benzisoxazine,1,4-benzisoxazine, anthracene, phenanthrene, carbazole, xanthene,acridine, purine, steroidal compounds and the like.

In a particularly preferred embodiment, S¹ through S⁴ are selected fromthe group consisting of phenyl, naphthyl, pyridinyl, and lower N-alkylpyridinium salts. Even more preferably, S¹ through S⁴ are identical.

In another embodiment, at least one of S¹ through S⁴ has the structure:##STR14## wherein X, Y, Z, X', Y' and Z' can be any one of a largenumber of substituents and are generally used to "fine tune" thebiological activity, the biodistribution, the absorption and clearancecharacteristics, and the physical properties of the desired product. Oneway in which this may be done by selecting substituents in such a mannerthat the compound of formula (I) or (II) is an amphiphilic molecule. By"amphiphilic" is meant the molecule becomes more asymmetric, such as

(1) having both (a) a highly polar, water-soluble region and (b) ahighly hydrophobic, water-insoluble region; or

(2) having both (a) a nonionic region and (b) an ionic region.

However, it should be noted that the invention also includesβ,β'-dihydroxy meso-substituted chlorin, bacteriochlorin orisobacteriochlorin compounds having substantially or exactly identicalaryl substituents. Further, any aryl substituent chosen should also haveno adverse effect on the ability of the compound to undergo the step"a." and step "b." reactions used to prepare the compounds of theinvention.

Preferably, X, X', Y, Y' and Z are independently (1) hydrogen; (2)halogen, such as fluoro, chloro, iodo and bromo; (3) lower alkyl, suchas methyl, ethyl, n-propyl, isopropyl, t-butyl, n-pentyl and the likegroups; (4) lower alkoxy, such as methoxy, ethoxy, isopropoxy, n-butoxy,t-pentoxy and the like; (5) hydroxy; (6) carboxylic acid or acid salt,such as --CH₂ COOH, --CH₂ COO-Na⁺, --CH₂ CH(Br)COOH, --CH₂ CH(CH₃)COOH,--CH(Cl)-CH₂ -CH(CH₃)-COOH, --CH₂ -CH₂ -C(CH₃)₂ -COOH, --CH₂ -CH₂-C(CH₃)₂ -COO⁻ K⁺, --CH₂ -CH₂ -CH₂ -CH₂ -COOH, C(CH₃)₃ -COOH, CH(Cl)₂-COOH and the like; (7) carboxylic acid ester, such as --CH₂ CH₂ COOCH₃,--CH₂ CH₂ COOCH₂ CH₃, --CH₂ CH(CH₃)COOCH₂ CH₃, --CH₂ CH₂ CH₂ COOCH₂ CH₂CH₃, --CH₂ CH(CH₃)₂ COOCH₂ CH₃, and the like; (8) sulfonic acid or acidsalt, for example, group I and group II salts, ammonium salts, andorganic cation salts such as alkyl and quaternary ammonium salts; (9)sulfonic acid ester, such as methyl sulfonate, ethyl sulfonate,cyclohexyl sulfonate and the like; (10) amino, such as unsubstitutedprimary amino, methylamino, ethylamino, n-propylamino, isopropylamino,5-butylamino, sec-butylamino, dimethylamino, trimethylamino,diethylamino, triethylamino, di-n-propylamino, methylethylamino,dimethyl-sec-butylamino, 2-aminoethanoxy, ethylenediamino,2-(N-methylamino)heptyl, cyclohexylamino, benzylamino, phenylethylamino,anilino, N-methylanilino, N,N-dimethylanilino, N-methyl-N-ethylanilino,3,5-dibromo-4-anilino, p-toluidino, diphenylamino,4,4'-dinitrodiphenylamino and the like; (11) cyano; (12) nitro; (13) abiologically active group; or (14) any other substituent that increasesthe amphiphilic nature of the compound of formula (I) or (II).

The term "biologically active group" can be any group that selectivelypromotes the accumulation, elimination, binding rate, or tightness ofbinding in a particular biological environment. For example, onecategory of biologically active groups is the substituents derived fromsugars, specifically, (1) aldoses such as glyceraldehyde, erythrose,threose, ribose, arabinose, xylose, lyxose, allose, altrose, glucose,mannose, gulose, idose, galactose, and talose; (2) ketoses such ashydroxyacetone, erythrulose, rebulose, xylulose, psicose, fructose,sorbose, and tagatose; (3) pyranoses such as glucopyranose; (4)furanoses such as fructofuranose; (5) O-acyl derivatives such aspenta-O-acetyl-α-glucose; (6) O-methyl derivatives such as methylα-glucoside, methyl β-glucoside, methyl α-glucopyranoside, andmethyl-2,3,4,6-tetra-O-methyl-glucopyranoside; (7) phenylosazones suchas glucose phenylosazone; (8) sugar alcohols such as sorbitol, mannitol,glycerol, and myo-inositol; (9) sugar acids such as gluconic acid,glucaric acid and glucuronic acid, δ-gluconolactone, δ-glucuronolactone,ascorbic acid, and dehydroascorbic acid; (10) phosphoric acid esterssuch as α-glucose 1-phosphoric acid, α-glucose 6-phosphoric acid,α-fructose 1,6-diphosphoric acid, and α-fructose 6-phosphoric acid; (11)deoxy sugars such as 2-deoxy-ribose, rhamnose (deoxy-mannose), andfucose (6-deoxy-galactose); (12) amino sugars such as glucosamine andgalactosamine; muramic acid and neurarninic acid; (13) disaccharidessuch as maltose, sucrose and trehalose; (14) trisaccharides such asraffinose (fructose, glucose, galactose) and melezitose (glucose,fructose, glucose); (15) polysaccharides (glycans) such as glucans andmannans; and (16) storage polysaccharides such as α-amylose,amylopectin, dextrins, and dextrans.

Amino acid derivatives are also useful biologically active substituents,such as those derived from valine, leucine, isoleucine, threonine,methionine, phenylalanine, tryptophan, alanine, arginine, aspartic acid,cystine, cysteine, glutamic acid, glycine, histidine, proline, serine,tyrosine, asparagine and glutamine. Also useful are peptides,particularly those known to have affinity for specific receptors, forexample, oxytocin, vasopressin, bradykinin, LHRH, thrombin and the like.

Another useful group of biologically active substituents are thosederived from nucleosides, for example, ribonucleosides such asadenosine, guanosine, cytidine, and uridine; and2'-deoxyribonucleosides, such as 2'-deoxyadenosine, 2'-deoxyguanosine,2'-deoxycytidine, and 2'-deoxythymidine.

Another category of biologically active groups that is particularlyuseful is any ligand that is specific for a particular biologicalreceptor. The term "ligand specific for a receptor" refers to a moietythat binds a receptor at cell surfaces, and thus contains contours andcharge patterns that are complementary to those of the biologicalreceptor. The ligand is not the receptor itself, but a substancecomplementary to it. It is well understood that a wide variety of celltypes have specific receptors designed to bind hormones, growth factors,or neurotransmitters. However, while these embodiments of ligandsspecific for receptors are known and understood, the phrase "ligandspecific for a receptor", as used herein, refers to any substance,natural or synthetic, that binds specifically to a receptor.

Examples of such ligands include: (1) the steroid hormones, such asprogesterone, estrogens, androgens, and the adrenal cortical hormones;(2) growth factors, such as epidermal growth factor, nerve growthfactor, fibroblast growth factor, and the like; (3) other proteinhormones, such as human growth hormone, parathyroid hormone, and thelike; and (4) neurotransmitters, such as acetylcholine, serotonin,dopamine, and the like. Any analog of these substances that alsosucceeds in binding to a biological receptor is also included.

Particularly useful examples of substituents tending to increase theamphiphilic nature of the compound of formula (I) include: (1) longchain alcohols, for example, --C₁₂ H₂₄ -OH where --C₁₂ H₂₄ ishydrophobic; (2) fatty acids and their salts, such as the sodium salt ofthe long-chain fatty acid oleic acid; (3) phosphoglycerides, such asphosphatidic acid, phosphatidyl ethanolamine, phosphatidyl choline,phosphatidyl serine, phosphatidyl inositol, phosphatidyl glycerol,phosphatidyl 3'-O-alanyl glycerol, cardiolipin, or phosphatidal choline;(4) sphingolipids, such as sphingomyelin; and (5) glycolipids, such asglycosyldiacylglycerols, cerebrosides, sulfate esters of cerebrosides organgliosides.

In a preferred embodiment, X, X', Y, Y' and Z are independentlyhydrogen, halogen, lower alkyl, lower alkoxy, hydroxy, carboxylic acidor acid salt, carboxylic acid ester, sulfonic acid or acid salt,sulfonic acid ester, substituted or unsubstituted amino, cyano, nitro,or a biologically active group, and Z' is hydrogen or lower alkyl. Inanother embodiment, X, Y, X' and Y' are each hydrogen, and Z is selectedfrom the group consisting of hydrogen, halogen, lower alkyl, loweralkoxy, hydroxy, carboxylic acid, carboxylic acid ester, sulfonic acidester (especially aromatic sulfonic acid ester), nitro, amino(especially lower alkyl amino), cyano, and a biologically active group.

In yet another embodiment, X, Y, Z, X' and Y' are selected from thegroup consisting of hydrogen, methyl, ethyl, t-butyl, methoxy, hydroxy,OR where R is an alkyl group or a fatty acid group having from 6 to 18carbon atoms, fluoro, chloro, iodo, bromo, --C(O)-OCH₃, cyano, nitro, ora ligand specific for a biological receptor. In a further preferredembodiment, X, X', Y and Y' and Z is selected from the group consistingof hydrogen, halogen, lower alkyl, lower alkoxy, hydroxy, carboxylicacid or acid salt, carboxylic acid ester, sulfonic acid ester, sulfonicacid or acid salt, nitro, amino, cyano, and a biologically active group.In still another preferred embodiment, at least one of X, Y, Z, X' andY' is a biologically active group or a substituent that increases theamphiphilic nature of the molecule.

Particularly preferred specific examples of groups that can serve as oneor more of S¹ through S⁴ include the following:

    __________________________________________________________________________     ##STR15##                                                                    X   X'     Y       Y'         Z                                               __________________________________________________________________________    H   H      H       H          H                                               OH  H      H       H          H                                               H   H      OH      H          H                                               H   H      H       H          OH                                              H   H      OH      OH         OH                                              H   H      H       H          SO.sub.3 H(Na)                                  CH.sub.3                                                                          CH.sub.3                                                                             H       H          CN                                              H   H      OCH.sub.3                                                                             OCH.sub.3  OCH.sub.3                                       H   H      H       H          COOH(Na)                                        H   H      COOH(Na)                                                                              COOH(Na)   H                                               H   H      H       H          C.sub.6 H.sub.12 COOH(Na)                       H   H      H       C.sub.6 H.sub.12 COOH(Na)                                                                H                                               H   H      C.sub.6 H.sub.13                                                                      H          SO.sub.3 H(Na)                                  H   H      H       COOH(Na)                                                   tert-Butyl                                                                    H   CH.sub.2 NH.sub.2                                                                    H       H          H                                               H   H      H       H          NH.sub.2                                        OH  H      H       H          CH.sub.2 NH.sub.2                               H   H      H       H          C.sub.4 H.sub.8 NH.sub.2                        H   H      H       COOCH.sub.3                                                                              COOH(Na)                                        OH  H      H       COONHCH.sub.3                                                                            H                                               H   H      H       COONHCH.sub.3                                                                            COOH(Na)                                        H   H      H                                                                  imidazoyl                                                                         H                                                                         H   H      H                                                                  glycinyl                                                                          H                                                                         H   H      H                                                                  steroidyl                                                                         H                                                                         H   H      H                                                                  glycosyl                                                                          H                                                                         H   H      H       H                                                          imidazoyl                                                                     H   H      H       H                                                          glycinyl                                                                      H   H      H       H                                                          steroidyl                                                                     H   H      H       H                                                          glycosyl                                                                      __________________________________________________________________________     ##STR16##                                                                    X   X'     Y       Y'         Z'                                              __________________________________________________________________________    H   H      H       H          H                                               H   H      H       H          CH.sub.3                                        H   H      H       H          C.sub.6 H.sub.12 OH                             H   H      H       OH         H                                               H   H      OH      H          H                                               H   H      H       COONHCH.sub.3                                                                            H                                               H   H      H       H                                                          benzyl                                                                        H   H      H       C.sub.6 H.sub.12 OH                                                                      CH.sub.3                                        H   H      C.sub.6 H.sub.13                                                                      H          CH.sub.3                                        __________________________________________________________________________     ##STR17##                                                                              Z"   Z"'                                                            __________________________________________________________________________              H    H                                                                        CH.sub.3                                                                           H                                                                        H    CH.sub.3                                                                 H    C.sub.6 H.sub.12                                                         C.sub.6 H.sub.12                                                                   H                                                              __________________________________________________________________________

Specific examples of such compounds include: ##STR18##

Examples of both cationic and anionic water soluble chlorin compoundsinclude: ##STR19##

Step "a." of the process of making the compounds of the inventioncomprises osmylating a meso-substituted metalloporphyrin of formula(III), or the corresponding demetallated porphyrinogenic of formula(IV), to form an osmate ester at the β,β'-position. The startingmeso-substituted metalloporphyrin (III) or porphyrin (IV) for thisreaction can be prepared by any one of a number of standard procedures.Examples include such techniques as:

(1) Pyrrole and appropriately substituted benzaldehydes can be reactedby the Adler method, in accordance with Adler et al., "A SimplifiedSynthesis for meso-Tetraphenylporphyrin", J. Org. Chem., 32, 476 (1967),or by the Lindsey method, as described in "Investigation of a Synthesisof meso-Porphyrins Employing High Concentration Conditions and anElectron Transport Chain for Aerobic Oxidation", J. Org. Chem., 59,579-87 (1994). Similar reactions are described for meso-tetraalkylcompounds in "Facile Syntheses of Tetraalkylchlorin andTetraalkylporphyrin Complexes and Comparison of the Structures of theTetramethylchlorin and Tetramethylporphyrin Complexes of Nickel (II), J.Am. Chem. Soc., 102:6852-54 (1980).

(2) The condensation of dipyrrolic compounds and their counterparts, asdescribed by Wallace et al., "Rational Tetraphenylporphyrin Syntheses:Tetraarylporphyrins from the MacDonald Route", J. Org. Chem., 58,7245-47 (1993).

(3) The manipulation of a porphyrin at its β- or meso-positions, forexample, as described by Di Magno et al., "Facile Elaboration ofPorphyrins Via metal-Mediated Cross-Coupling", J. Org. Chem., 58,5983-93 (1993); or by Osuka et al., "Synthesis of5,15-Diaryl-Substituted Oxochlorins from 5,15-Diaryl-octaethylPorphyrin, Bull. Chem. Soc. Japan, 66, 3837-39 (1993); or themanipulation of phenyl substituents on a preexisting and appropriatelysubstituted meso-phenylporphyrins described by Hombrecher et al., "AnEfficient Synthesis of Tetraaryl Porphyrins Substituted with EsterGroups Bearing Long Alkyl Chains", Tetrahedron, 49:12, 2447-56 (1993).

The disclosures of all of the above documents are hereby incorporated byreference.

Preferably, the compound of formula (III) used as the starting materialfor step "a." is prepared by using the Lindsey et al. method forsynthesizing porphyrins (see above). A general procedure for carryingout such a reaction is set forth below: Typically, an equimolar mixtureof pyrrole and an appropriately substituted benzaldehyde are reactedunder a nitrogen atmosphere with acid catalysis. Oxidation of the formedporphyrinogen with air or treatment with DDQ as an oxidant gives theporphyrin, which is then typically purified by column chromatography.

The osmylation reaction of step "a." is be carried out by treating thestarting material with OsO₄ in the presence of a base, typicallypyridine, thus forming an osmate ester at the β,β'-position, as shownbelow: ##STR20##

The amount of the OsO₄ is generally stoichiometric, and typically variesfrom about 1.0 to about 1.5 moles OsO₄ per mole of starting material.

The base usually used with the OsO₄ is generally one that is able tocoordinate to the osmium(IV) in the osmate ester and that, thereby,stabilizes this intermediate and speeds up the formation of the osmateester. See, for example, Schroder, "Osmium Tetroxide Cis Hydroxylationof Unsaturated Substrates", Chem. Rev., 80:187-218 (1980). Preferredbases include pyridine, imidazole, isoquinoline, tert-alkyl amines suchas trimethylamine, methylsulfonamide and the like. The amount of baseused can vary widely, so long as a sufficient amount is present saturatethe coordination sphere of the osmium(VI) in the osmate ester.Preferably, however, the amount of base used falls within the range ofabout 2 to about 20 equivalents. Some bases, such as pyridine, can alsobe used as solvents or co-solvents for the osmylation reaction.

While the OsO₄ can be added to a reaction mixture neat, it is best useddissolved in a suitably non-reactive solvent. When used, the choice of asolvent depends on the substituent pattern on the porphyrin startingmaterial, which affects its solubility. However typically encounteredsolvents include aromatic solvents, such as pyridine, toluene andbenzene; chlorinated solvents, such as CHCl₃ and dichloromethane; water;ethers, such as diethyl ether, tetrahydrofuran, diethylene glycol andglycol dimethyl ether (ethylene glycol dimethyl ether); ketones such asacetone and methyl ethyl ketone; acetonitrile; DME, DMF and DMSO;alcohols such as ethanol, methanol and butanol; and mixtures thereof.

When the starting material is water-soluble, the preferred solvent iswater. When an organic solvent is used, particularly useful solventsystems include combinations of chlorinated solvents, such as CHCl₃ anddichloromethane, mixed with about 2-25 volume % pyridine.

The temperature of the reaction mixture during step "a." can vary widelybut, typically, is maintained at room temperature or cooled somewhat toa temperature in the range of about -10° C. to room temperature.Preferably, the reaction is carried out at about room temperature.

The time required for the osmylation reaction of step "a." will dependto a large extent on the temperature used and the relative reactivitiesof the starting materials. Particularly when the meso-substituents arearyl or a bulky alkyl group, such as tert-butyl, the reaction time tendsto be relatively slow due to steric hindrance of the β-positions againstthe attack of the incoming osmium (VIII) species of OsO₄ (complexed witha base such as pyridine). Thus, even though di-meso-substituted systemshave been observed to react relatively quickly, the tetra-substitutedsystems, at least where one or more of S¹ through S⁴ are particularlybulky such as a tert-butyl group, a cycloalkyl group, or a substitutedphenyl ring, may require a significantly longer time to go tocompletion. Therefore, the reaction time can vary greatly, for example,from about 1 hour to about 7 days.

The osmylation reaction can be carried out at pressures both above andbelow atmospheric pressure. Preferably, however, the reaction is carriedout at a pressure about equal to atmospheric pressure. The reaction canbe carried out in the presence of a mixture of gases approximating airbut, when particularly reactive reactants are involved, the gaseousmixture may be enriched with an inert gas, such as nitrogen gas, argon,and the like.

The osmylation step of the invention can be carried out under conditionsof normal, ambient lighting. However, because the substrates andproducts of the osmylation are often good photosensitizers, theexclusion of light is generally preferred to minimize side reactions.

The progress of the reaction sometimes involves a color change of thereaction mixture, for example, from purple to green. If desired, thiscolor change can be used to monitor the approximate degree of completionof the reaction. Other known techniques, such as various types ofchromatography, especially TLC and HPLC, can also be used to follow theprogress of the reaction by the disappearance of the starting material.

At the conclusion of the osmylation reaction, a reaction mixtureresults, from which the diol product is separated and purified by anyconventional means, typically chromatographically. Preferably, however,the osmylation reaction mixture is used directly in the reduction step"b." without the intervening isolation or purification of theintermediate(s) present in the reaction mixture being necessary.

The reduction of the osmylation reaction mixture to form the diol offormula (I) can be accomplished by many of the usual reducing agents.Examples of such useful reducing agents include gaseous H₂ S, HSO₃ ⁻,BH₄ ⁻, AlH₄ ⁻, B₂ H₆, H₂ with a Ni- or Pd- catalyst, Zn/H+ and the like.However, particularly convenient reductants include H₂ S and HSO₃ ⁻, ofwhich H₂ S is more preferred.

Most of the above reducing agents are used in combination with asuitably non-reactive organic or inorganic non-solvent, such asmethanol, ethanol and the like, to aid in solubilizing the polardihydroxylated product, especially when the product is an anionic orcationic species. A co-solvent sometimes also facilitates the isolationand purification of the product. A particularly preferred combination ofreducing agent and non-solvent for step "b." is H₂ S with methanol.

Specific examples of reducing agents that are particularly useful fordirect addition to the reaction mixture at the end of the osmylationstep "a.", without the intervening isolation or purification of specificcompounds in the osmylation reaction mixture, include: (1) treatmentwith H₂ S and methanol; and (2) vigorous stirring of the organic phasewith a solution of HSO₃ ⁻ in H₂ O. In such cases, reduction may proceedat a satisfactory rate, as commonly occurs with the first method, or thereaction may occur dependably but at rate that may be significantlyslower, as sometimes occurs with the second method. Thus, the rate ofthe reaction is often influenced by the type and combination of reducingagent, with or without the presence of a non-solvent to precipitate outthe unused reducing agent.

The temperature of the reaction mixture during the reduction step "b."can vary widely depending upon the reducing agent being used. Forexample, when gaseous H₂ S is being used as the reducing agent, thetemperature is typically allowed to remain at about room temperature.When other reducing agents, however, the temperature can range fromabout 1° to about 100° C.

The time required for the reduction reaction of step "b." will depend toa large extent on the temperature used and the relative reactivities ofthe starting materials but, preferably, is about room temperature. Thereduction reaction of step "b." can be carried out in the presence ofgases at a pressure both above and below atmospheric pressure. Mostfrequently, however, the reaction is carried out at a pressure aboutequal to atmospheric pressure.

The resulting product, a β,β'-dihydroxy meso-substituted chlorin,bacteriochlorin or isobacteriochlorin compound of formula (I) or formula(II), can be isolated by any conventional method, such as by drowningout in a non-solvent, precipitating out, extraction with any immiscibleliquid, evaporation of a solvent, or some combination of these or otherconventional methods. Typically, the β,β'-dihydroxy compound of formula(I) or formula (II) may then be purified by any one or a combination ofknown purification techniques, such as recrystallization, various formsof column chromatography, trituration with a non-solvent or a partialsolvent, countercurrent extraction techniques, and the like.

A general procedure for accomplishing a typical osmylation-reduction isset forth below:

A known amount of 5,10,15,20-meso-tetraphenylporphyrin is suspended in asolvent mixture of about 40:1 CHCl₃ :pyridine and mixed with 1.3equivalents OsO₄. The reaction mixture is stirred in the dark for about4 days. The reaction is quenched by purging with gaseous H₂ S for a fewminutes. After adding methanol, the precipitated black OsS is filteredoff. The filtrate is evaporated to dryness, chromatographed, forexample, on silica/CH₂ Cl₂ -0.5% methanol, and further purified byrecrystallization.

Where the demetallated β,β'-dihydroxy compound of formula (II) isdesired, demetallation can take place at one of several stages duringthe process of the invention. One can either (1) start with thedemetallated meso-substituted porphyrinogenic compound having theformula (IV) shown below: ##STR21## or (2) osmylate the meso-substitutedmetalloporphyrin and remove the metal M from the compounds making up thereaction mixture after the osmylating step "a" and prior to the reducingstep "b"; or (3) demetallate the β,β'-dihydroxy meso-substitutedcompound of formula (I) after the reducing step "b" to form a compoundof formula (II).

The presence of the metal M is not generally required to carry outeither the osmylation step "a" or the reduction step "b". However, inmany cases, having a metal ion present increases the solubility of thestarting material of the reaction, thus enabling a higher concentrationof reactants and a shorter reaction time. Therefore, it is believed tobe advantageous to have the metal present, particularly during theosmylation step "a" of the process of the invention. However, it shouldbe noted that, in addition to the metal, other substituents on themeso-substituted compound may also have a significant effect on thesolubility of the compound and thus also influence the concentration andreaction time.

Whether the β,β'-dihydroxy compound of formula (I), or the correspondingcompounds after the osmylating step "a", or the corresponding compoundsafter the reduction step "b", are being demetallated, the reactionconditions are usually the same or very similar. Suitable demetallatingreagents used for this purpose include any acid that is capable ofdemetallating, but which does not induce the formation ofoxo-porphyrins. Also the demetallating conditions should be selected tobe compatible with the particular substituents present on the compoundbeing demetallated.

Typically, concentrated mineral acids, such as sulfuric acid andhydrochloric acid should be avoided because they are often sufficientlyharsh to rearrange/dehydrate the diol substrate to form thecorresponding oxo-porphyrin, as well as demetallating the compound.Preferably, the demetallating agent is selected from the groupconsisting of CH₃ COOH, CF₃ COOH, H₂ S, 1,3-propanedithiol, dilutehydrochloric acid in a suitable solvent such as water or chloroform, andmixtures thereof. Examples of suitable mixtures of demetallating agentsinclude: (1) dilute trifluoroacetic, (2) H₂ S, and (3) a two-phasesystem formed by chloroform and dilute (5%) aqueous hydrochloric acid.

Although demetallation reactions are known to those of ordinary skill inthis art, additional information can be obtained in J. W. Buchler,"Synthesis and Properties of Metalloporphyrins", The Porphyrins, Vol. I,Chapter 10 (2978). The above demetallating agents can sometimes be usedin combination with a suitably non-reactive solvent. Examples of usefulsolvents include water; alcohols, such as ethanol, methanol,iso-propanol and the like; haloalkanes such as methylene chloride andthe like; nitrogen-containing solvents such as DMF, tetrahydrofuran andthe like; relatively unreactive aromatic compounds such as benzene,toluene and the like; and ethers such as diethyl ether, diethyleneglycol, and glycol dimethyl ether.

The temperature of the reaction mixture during the demetallating processcan vary widely but, typically, is maintained in the range of about 0°to 120° C. For example, refluxing acetic acid can be used as ademetallating agent in some circumstances, which would provide atemperature of about 118° C. However, the demetallating reaction is mostpreferably carried out at about room temperature or below.

The time required for demetallation varies widely, depending on thetemperature used and the relative reactivities of the startingmaterials, particularly the demetallating agents and the metal to beremoved from the porphyrin. For example, when a two-phase system of 5%aqueous hydrochloric acid and chloroform is used to demetallate a zincporphyrin, the reaction typically takes place in minutes. If, on theother hand, rearrangement is desirable, the metallated compound can besubjected to stronger acid conditions, such as dry hydrochloric gas inchloroform, to accomplish the rearrangement, remove the metal, or both.

The reaction can be carried out above or below atmospheric pressure.Preferably, the reaction is carried out at a pressure about equal toatmospheric pressure. Straightforward procedures can be used to isolatethe demetallated product, such as neutralization of the reactionmixture, extraction with any immiscible liquid, eluting on a silica gelcolumn or other types of chromatography, drowning out in a non-solvent,precipitating out or otherwise crystallizing, evaporation of solvent, orsome combination of these or other conventional methods. Preferredmethods of isolating the desired demetallated compound includechromatography and/or crystallization. If further purification of thedemetallated product is desired, it may be subjected to additionalpurification procedures, such as recrystallization, eluting on a silicagel chromatography column, and combinations of these methods.

Because of the mechanism of the OsO₄ oxidation of olefins, theβ,β'-dihydroxy compounds resulting from step "a." and step "b." arevicinal diols. The introduction of the vic-diol gives the molecule anamphiphilic character, a property believed to be important in thebiodistribution of site-specific photochemotherapeutics. Moreover, theconversion of a porphyrin into a chlorin changes the optical propertiesin a desirable direction (tetraphenyl porphyrin, λ_(max) [benzene]=653nm, log ε=3.80; 2,3-vic-dihydroxy-tetraphenylchlorin, λ_(max) [CH₂ Cl₂-0.1% MeOH]=644 nm, log ε=4.38). Converting the dihydroxy chlorin intothe tetrahydroxy bacteriochlorin, this effect is even more pronounced(2,3,12,13-tetrahydroxy bacteriochlorin, λ_(max) [CH₂ Cl₂ -0.5%MeOH]=708 nm, log ε=4.89). This increase in the log ε values of λ_(max)means that the chlorin absorbs light about 4.0 times more efficiently inthe red region of the spectrum than the parent porphyrin, as a result ofintensified Q bands.

Further still, the compounds of the invention are surprisingly stabletoward dehydration and concomitant reconstitution of the porphyrinchromophore. For example, it has now been found that dilute HCl in CHCl₃under reflux conditions can be successfully used to demetallate achlorin of formula (I) where M is Zn, but without provoking undesirablerearrangement reactions. To purposely accomplish the expecteddehydration and rearrangement to the corresponding oxo compound, asshown below, a catalytic amount HClO₄ must also be added. ##STR22##

Likewise, when meso-tetraphenylchlorin is treated with a stoichiometricamount of OsO₄, followed by reduction of the intermediate, the2,3-vic-dihydroxy-meso-tetraphenylbacteriochlorin is produced. However,insertion of Zn(II) as a metal ion into the chlorin changes the outcometo yield, instead, the (2,3-vic-dihydroxyisobacteriochlorinato)Zn.sup.Π, which can be demetallated under mild acidic conditions toproduce 2,3-vic-dihydroxyisobacteriochlorin. This sequence of reactionsis shown schematically below to illustrate again the directing effect ofthe central metal when present. ##STR23##

The reason for this phenomenon is not well-understood. Some havesuggested that the reduced double bond in a chlorin compound induces apathway for the delocalized π-electrons that "isolates" thediametrically opposed pyrrolic double bond. Attack is thought to befavored here over the attack of the double bond in the adjacent pyrrolicunit, as it causes a minimal loss of π-energy, leading to the selectiveformation of a bacteriochlorin compound. The introduction of a metal (orthe protonation of the chlorin), it is thought, would cause a change ofthe preferred π-localizing pattern, "isolating" the double bond on anadjacent pyrrolic unit and resulting in the formation of ametallo-isobacteriochlorin.

The β,β'-dihydroxy meso-substituted chlorin, bacteriochlorin andisobacteriochlorin compounds of the invention can also be subjected toreaction steps "a" and "b" a second time to add a second pair of hydroxygroups. The relative position of the second pair of hydroxy groupsdepends on many factors, such as the presence of a metal, the selectionof the metal when one is present, the relative bulk and electroniccharacteristics of the meso-substituents, and the presence andcharacteristics of additional β,β'-substituents.

Of particular interest, again, is the role of the metal M in directing asecond pair of hydroxy substituents to preferred positions. For example,when a demetallated diol chlorin of formula (II) is osmylated andreduced in accordance with the process of the invention, the second pairof hydroxy groups goes to the β,β'-positions on the opposite ring.Conversely, if a metallated compound of formula (I) is used, e.g., onewhere M is zinc, the second pair of hydroxy groups is added to theβ,β'-positions of an adjacent ring. This phenomenon has also beenobserved with respect to other reactions, for example, in the diimidereduction of porphyrins described in Whitlock et al., "Diimide Reductionof Porphyrins", J. Am. Chem. Soc., 91, 7485-89 (1969); in the OsO₄oxidation of octaalkyl chlorins described in Chang et al., J. Chem.Soc., Chem. Comm., 1213-15 (1986); in the Raney nickel-catalyzedreduction of Ni.sup.Π pheophorbides as described in Smith et al., J. Am.Chem. Soc., 107, 4954-55 (1985); and in the OsO₄ oxidation ofpheophorbides described in Pandey et al., Tetrahedron Lett., 33, 7815-18(1992).

When a diol chlorin is β,β'-dihydroxylated, a 1:1 mixture of two isomersof 2,3,12,13-bis-(vic-dihydroxy)bacteriochlorins are formed, as shownbelow. ##STR24## The isomer carrying the hydroxyl groups on one side ofthe plane of the porphyrin is, due to its higher polarity, separablefrom its isomer by column chromatography. This isomer has a pronouncedamphiphilic character from bearing all polar functionalities on one sideof the molecule. The absorption characteristics of the hydroxybacteriochlorins are in a "preferred" range for use as photosensitizersin photodynamic therapy.

When the corresponding zinc-metallated diol chlorin is furtherβ,β'-dihydroxylated, the result is a 1:3 mixture of tetraolmetalloisobacteriochlorins (the lower structure being more prevalent),as shown below: ##STR25## While not completely understood at this time,steric reasons are believed to cause this deviation from a 1:1 mixture.The lower compound (C₂ point group) occurs as a racemic mixture, whilethe upper compound (C_(S) point group) is not chiral.

The β,β'-dihydroxy meso-substituted chlorin, bacteriochlorin orisobacteriochlorin compounds of the invention can also be dehydratedunder acid catalysis to form the corresponding2-oxy-(meso-tetraphenyl)porphyrins, if desired, thus forming thebeginning of yet another synthetic pathway to this known class ofcompounds. While a few of these compounds are accessible via othermethods, e.g. Catalano et al., "Efficient Synthesis of2-Oxy-5,10,15,20-tetraphenylporphyrins from a Nitroporphyrin by a NovelMultistep Cine-substitution Sequence", J. Chem. Soc., Chem. Comm.,1537-38 (1984), many other compounds can be prepared via thedihydroxylation method of the invention. Specific examples of suchcompounds are shown below and include:

(A) 2-oxy-12,13-dihydro-meso-tetraphenyl porphyrin;

(B) 2-oxy-7,8-dihydro-meso-tetraphenyl porphyrin; and

(C) 2,12-dioxo-meso-tetraphenyl porphyrin. ##STR26## Other syntheticpathways of potential interest include the formation of a isopropylideneketal, which may confer the ability to fine tune solubilities,biodistribution properties and amphiphilicities of the compounds of theinvention even further, and without losing valuable spectral qualities.

The β,β'-dihydroxy meso-substituted chlorin, bacteriochlorin andisobacteriochlorin compounds of the invention are useful asphotosensitizers used in photodynamic therapy (PDT) and as syntheticintermediates for making related photosensitizers. Specifically, thesephotosensitizers are useful in sensitizing neoplastic cells or otherabnormal tissues to destruction by irradiation with visible light. Uponphotoactivation, the energy of photoactivation is believed to betransferred to endogenous oxygen, thus converting it to singlet oxygen.This singlet oxygen is thought by some to be responsible for theobserved cytotoxic effect. Alternatively, there may be direct electrontransfer from the photoactivated molecule. The method of van Lier,Photobiological Techniques, 216, 85-98 (Valenzo et al. eds. 1991) can beused to confirm the ability of any given compound to generate singletoxygen effectively, thus making it a good candidate for use inphotodynamic therapy. In addition, the photoactivated forms of porphyrinare able to fluoresce, and this fluorescence can aid in imaging a tumor.

Typical indications known in the art include diagnosis and destructionof tumor tissue in solid tumors, such as those of bronchial, cervical,esophageal or colon cancer; dissolution of plaques in blood vessels(see, e.g., U.S. Pat. No. 4,512,762, which is hereby incorporated byreference); treatment of topical conditions such as acne, athlete'sfoot, warts, papilloma and psoriasis; and treatment of biologicalproducts, such as blood for transfusion to eliminate infectious agents.

Additionally, when metals such as In or Tc are used, the metallatedpigment compounds of the invention have diagnostic use in nuclearmedicine. Similarly, when M is Mn(III) or Gd(III), the compounds may beuseful in magnetic resonance imaging. These are also applications where,due the variability possible with respect to the substitution patterns,significantly improved biodistribution properties may be achieved byusing the compounds of the invention.

The photosensitizers made from the compounds of the invention can beformulated into pharmaceutical compositions for administration to thesubject or applied to an in vitro target using techniques generallyknown in the art. A summary of such pharmaceutical compositions may befound, for example, in Remington's Pharmaceutical Sciences, MackPublishing Co., Easton, Pa. The compounds of the invention can be usedsingly or as components of mixtures.

Generally, for the diagnosis or treatment of solid tumors, the compoundof the invention, labeled or unlabeled, is administered systemically,such as by injection. Injection may be intravenous, subcutaneous,intramuscular, or even intraperitoneal. Injectables can be prepared inconventional forms, either as liquid solutions or suspensions, solidforms suitable for solution or suspension in a liquid prior toinjection, or as emulsions. Suitable excipients are, for example, water,saline, dextrose, glycerol and the like. Of course, these compositionsmay also contain minor amounts of nontoxic, auxiliary substances, suchas wetting or emulsifying agents, pH buffering agents, and so forth.

Systemic administration can be implemented through implantation of aslow release or sustained release system, by suppository, or, ifproperly formulated, orally. Formulations for these modes ofadministration are well known in the art, and a summary of such methodsmay be found, for example, in Remington's Pharmaceutical Sciences(supra).

If treatment is to be localized, such as for the treatment ofsuperficial tumors or skin disorders, the compound can be administeredtopically using standard topical compositions, such as lotions,suspensions, or pastes.

The quantity of the photosensitizer compound to be administered dependsupon the choice of active ingredient, the condition to be treated, themode of administration, the individual subject, and the judgment of thepractitioner. Depending on the specificity of the preparation, smalleror larger doses may be needed. For compositions that are highly specificto target tissues, such as those with a highly specific monoclonalimmunoglobulin preparation or a specific receptor ligand, dosages in therange of 0.05-1 mg/kg are suggested. For compositions that are lessspecific to the target tissue, larger doses, up to 1-10 mg/kg may beneeded. The foregoing ranges are merely suggestive, as the number ofvariables in regard to an individual treatment regime is large, andconsiderable excursions from these recommended values are not uncommon.

In addition to in vivo use, the compounds made from the intermediatecompounds of the invention can be used in the treatment of materials invitro to destroy harmful viruses or other infectious agents. Forexample, blood plasma or blood that is to be used for transfusion orbanked for future transfusion, can be treated with the compounds of theinvention and irradiated to effect sterilization. In addition,biological products such as Factor VIII, which are prepared frombiological fluids, can be irradiated in the presence of the compounds ofthe invention to destroy contaminants.

Further, because the S¹ through S⁴ groups in the four meso positions canbe the same or different, or substituted either symmetrically orasymmetrically, the compounds of the invention can be "fine tuned" toproduce a desired set of biological effects when administered to asubject in need of photodynamic therapy. As a specific example, to "finetune" the solubility, biodistribution, and/or amphiphilicities of thecompounds of the invention, the corresponding isopropylidene ketal maybe formed. Further still, the invention provides methods forsynthesizing such derivative compounds in an efficient manner withrelatively few by-products or isomeric impurities.

The invention will be further clarified by the following examples, whichare intended to be purely illustrative of the invention.

Example 1: β,β'-Dihydroxylation of Tetraphenylporphyrin to Make3,4-Dihydroxy-5,10,15,20-tetraphenylchlorin ##STR27##

1.00 g (1.63×10⁻³ mol) of 5,10,15,20-meso-tetraphenylporphyrin wassuspended in 200 ml of freshly distilled, ethanol-stabilized CHCl₃. Theresulting mixture was treated with 5.0 ml freshly distilled pyridine and540 mg (2.12×10⁻³ mol, 1.3 equivalents) OsO₄. The reaction flask wasstoppered and stirred at room temperature in the dark for four days. Thereaction was quenched by purging with gaseous H₂ S for five minutes.Following the addition of 20 ml of methanol, the precipitated black OsSwas filtered off through diatomaceous earth (commercially availableunder the trade name Celite). The filtrate was evaporated to dryness,and the residue was charged onto a silica gel column (200 g, 280-400mesh) and eluted with 1,1-dichloromethane to remove the unreactedstarting material (400 mg, 40%). A mixture of 1.5% methanol in1,1-dichloromethane was used to elute the desired β,β'-dihydroxychlorinproduct (520 mg, 8.02×10⁻⁴ mol, 49% yield). Finally, 5.0% methanol indichloromethane eluted a crude mixture of tetrahydroxybacteriochlorins(40 mg, 3.5 %). The desired β,β'-dihydroxychlorin was recrystallized inCHCl₃ /methanol, m.p. >350° C. The UV-vis spectrum of thisβ,β'-dihydroxychlorin was typical for chlorins and is shown in FIG. 1.

R_(F) =0.68 (silica gel, CH₂ Cl₂ /1.5% methanol);

¹ H NMR (400 MHz, CDCl₃) δ=-1.78 (br s, 2H, NH); 3.14 (s, 2H, OH,exchangeable with D₂ O); 6.36 (s, 2H, pyrroline-H); 7.68-7.80 (m, 12H,phenyl-(m,p) -H); 7.92 (d, J=8.5Hz, 2H, phenyl-H); 8.09 (br s, 4H,o-phenyl-H); 8.15 (d, J=8.5Hz, 2H, o-phenyl-H); 8.33 (d, J=7.9Hz, 2H,β'-H); 8.48 (s, 2H, β-H); 8.63 (d, J=7.9Hz, 2H, β"-H);

¹³ H NMR (125 MHz, CDCl₃)δ=73.9, 113.2, 123.1, 124.2, 126.7, 127.5,127.7, 127.9, 128.1, 132.2, 132.7, 133.9, 134.1, 135.5, 140.6, 141.2,141.8, 153.2, 161.4;

UV-Vis (CH₂ Cl₂ -0.1% MeOH): λ[nm] (log ε) 408 (5.27) , 518 (4.19), 544(4.19), 592 (3.85), 644 (4.38);

Fluorescence at 649 nm (excitation wavelength at 408 nm, 1.10×10⁻⁶ M inCH₂ Cl₂);

LR-MS (EI, 300° C.)m/e (%): 648 (0.5,M⁺); 646 (0.9,M⁺ -2H); 630 (100,M⁺-H₂ O), 614 (42.7);

HR-MS (EI, 250° C.): calc'd for C₄₄ H₃₂ N₄ O₂ : 648.2525; found648.2525;

Analysis calculated for C₄₄ H₃₂ N₄ O₂.1/2 H₂ O: C, 80.34; H, 5.06; andN, 8.52; found: C, 80.26; H, 4.93; and N, 8.46.

Example 2: β,β'-Dihydroxylation of Tetraphenylporphyrin to Make3,4-Dihydroxy-5,10,15,20-tetraphenylchlorinatozinc(II) ##STR28##

The preparation of the zinc metallated compound analogous to thecompound of Example 1 above is based on the procedure of Example 1,except for being adapted to the higher solubility of the metallatedstarting compound, 5,10,15,20-meso-tetraphenylporphyrinato-zinc(I). 520mg (7.37×10⁻⁴ mol) of the starting compound was dissolved in 20 ml offreshly distilled, ethanol-stabilized CHCl₃, and treated with 5.0 mlfreshly distilled pyridine and 225 mg (8.84×10⁻⁴ mol, 1.2 equivalents)OsO₄. The reaction flask was stoppered and stirred at ambienttemperature in the dark for 14 hours. The reaction was quenched bypurging with gaseous H₂ S for five minutes. Following the addition of 3ml methanol, the precipitated black OsS was filtered off through a padof diatomaceous earth (commercially available under the trade nameCelite). The filtrate was evaporated to dryness, and the resultingresidue was charged onto a silica gel column (100 g, 280-400 mesh) andinitially eluted with dichloromethane to remove the unreacted startingmaterial (55 mg, 111). A mixture of 0.5% methanol in dichloromethane wasused to elute the desired β,β'-dihydroxy metallochlorin product (380 mg,5.34×10⁻⁴ mol, 72% yield). The desired β,β'-dihydroxy metallochlorin wasrecrystallized in CHCl₃ /methanol, m.p. >350° C. The UV-vis spectrum ofthe β,β'-dihydroxy metallochlorin was typical for metallochlorins and isshown in FIG. 1.

R_(F) =0.62 (silica gel, 1.51 methanol in CH₂ Cl₂ ;

¹ H NMR (300 MHz, CDCl₃) δ=5.30 (s, 2H, OH, exchangeable with D₂ O);6.12 (s, 2H, pyrrolidine-H); 7.55-7.72 (m, 12H, phenyl-H); 7.81 (dd,J=1.4, 7.5Hz, 2H, phenyl-H); 7.97-8.06 (m, 4H, phenyl-H); 8.08 (d,J=4.5Hz, 2H, β-H), 8.10-8.15 (br m, 2H, phenyl-H); 8.37 (s, 2H, β-H);8.48 (d, J=4.5Hz, 2H,

¹³ H NMR (75 MHz, CDCl₃): δ=50.633,126.482, 126.585, 126.629, 127.226,127.351, 127.479, 127.684, 127.766, 127.815, 129.307, 132.114, 132.523,133.628, 133.680, 133.789, 141.729, 142.573, 146.516, 148.038, 154.217,156.279;

UV-Vis (CH₂ Cl₂ -0.1% MeOH): λ[nm] (log ε) 418 (5.41), 614 (4.71);

Fluorescence at 620 nm (excitation wavelength at 418 nm, 1.18×10⁻⁶ M inCH₂ Cl₂);

LR-MS (+FAB, 3-NBA)m/e (%): 710 (29.2,M⁺); 693 (7.0,M⁺ -OH); 676 (3.7,M⁺-2OH);

HR-MS (+FAB, 3-NBA): calc'd for C₄₄ H₃₀ N₄ O₂ Zn: 710.16602; found710.16595;

Analysis calculated for C₄₄ H₃₀ N₄ O₂ Zn.1/2H₂ O.1/2C₅ H₅ N: C, 73.42;H, 4.44; and N, 8.29; found: C, 73.50; H, 4.25; and N, 7.87.

Example 3: The Synthesis of a Water Soluble Chlorin,2,3-Dihydroxy-5,10,15,20-tetra-(4-pyridyl)-chlorinato zinc(II) ##STR29##

The product compound of Example 3 was prepared analogously to thegeneral procedure of Example 2:

R_(F) =0.12 (silica gel, CH₂ Cl₂ /10.0% MeOH/2.0% pyridine);

UV-Vis(CH₂ Cl₂): λ_(max) =408 (sh), 424 (Soret), 526, 570, 598, 629 nm;

MS (+FAB, thioglycerol) m/e (%): 715 (56, M⁺ +H) , 697 (27, M⁺ +H-H₂ O);

MS (+FAB, thioglycerol) calc'd for C₄₀ H₂₆ N₈₀ 2Zn: 714.14702, found:714.15401.

Example 4: Preparation ofcis-2,3-Dihydroxy-5,10,15,20-tetraphenylbacteriochlorin ##STR30##

The compound above was prepared according to the general procedure ofExample 1. Thus, tetraphenylporphyrin was oxidized with 1.22 equivalentsof OsO₄ over a two-day period. The oxidation reaction was quenched withH₂ S, and the product was chromatographically purified. Yield: 53%:

R_(F) =0.78 (silica gel, 2.5% MeOH/CH₂ Cl₂);

¹ H NMR (400 MHz, CDCl₃) δ=-1.58 (s, 2H, NH); 3.00 (s, 2H, OH);3.94-4.21 (m, 4H, pyrrolin-2, 3-H); 6.13 (s, 2H, pyrrolin-12, 13-H);7.58-7.73 (m, 12H, phenyl^(A),B -(m,p)-H); 7.79 (br tr, J=6.8Hz, 4H,phenyl^(A) -o-H); 7.86 (br d, J=4.4Hz, 2H, phenyl^(B) -o-H); 7.97 (dd,J=4.8, 2Hz, 2H, phenyl^(B) -o-H); 8.13 (2 overlapping d-2nd order, 4H,(β',β") -H);

UV-Vis (CH₂ Cl₂ -0.5% MeOH): λ[nm] (log ε) 378 (4.96), 524 (4.49), 724(4.71);

LR-MS (+FAB, 3-NBA) m/e(%): (100, M⁺), 633 (19.2, M⁺ -OH).

HR-MS (+FAB, 3-NBA): calc'd for C₄₄ H₃₄ N₄ O₂ : 650.26818; found650.27118.

Example 5: Preparation of the Two IsomericTetrahydroxytetraphenylbacteriochlorins, 2R,3S,12R,13S-Tetrahydroxy-5,10,15,20-tetra phenylbacteriochlorin and2R,3S,12S,12R-Tetrahydroxy-5,10,15,20-tetraphenylbacteriochlorin##STR31##

100 mg of the starting compound above (1.54×10⁻⁴) were dissolved in aminimal amount of CHCl₃ containing 10% pyridine (ca. 4 ml). 51 mg OsO₄(1.3 equivalents) were added, and the stoppered solution was stirred atroom temperature until the chlorin peak at 644 nm was largely replacedby the bacteriochlorin peak at 708 nm (16 hours). The oxidation reactionwas quenched by bubbling gaseous H₂ S through the reaction mixture.After filtering the solution to remove the resulting precipitate, thesolvent was removed from the filtrate by evaporation. The resultingmixture was separated on a prepared TLC plate (silica gel, 2 mm, 5% MeOHin CH₂ Cl₂ as eluent, two developments). The purplish starting compoundmoved more quickly, almost simultaneously with the solvent front, whilethe dark pink bacteriochlorins followed with:

E-isomer: R_(f) (silica gel, 5% MeOH in CH₂ Cl₂)=0.51

Z-isomer: R_(f) (silica gel, 5% MeOH in CH₂ Cl₂)=0.30

After isolation and recrystallization in CH₂ Cl₂ /hexane, the combinedyields were 40%. The two isomers occurred in a 1:1 ratio (21 mg ofeach).

Because the symmetry groups of the two isomers, C_(2v) and C_(2h),respectively, did not allow distinction based on NMR, UV-Vis, or MS,tentative assignment of the E-isomer or the Z-isomer structure to theindividual bacteriochlorins was made based on their chromatographicbehavior. The compound with both sets of hydroxy functionalities on thesame side of the porphyrin plane (`Z-relationship`) was assumed to bemore polar than where the two sets of hydroxy functionalities have an`E-relationship`.

E-isomer:

R_(F) =0.51 (silica gel, CH₂ Cl₂ /5.0% MeOH);

¹ H NMR (300 MHz, DMSO-d₆): δ=-1.65 (s, 2H, NH); 4.99 (d, J=4.9Hz, 4H,OH); 5.87 (d, J=4.9Hz, 4H, pyrrolidin-H); 7.6 (br m, 12H, phenyl m-,p-H); 7.86 (br(s), 4H, β-H); 7.96 (d, J=1.8Hz, 8H, phenyl-o-H);

¹³ C NMR (75 MHz, DMSO-d₆): δ=73.112, 115.631, 122.879, 127.100,131.537, 133.852, 136.223, 141.217, 160.067;

UV-Vis (CH₂ Cl₂ -0.5% MeOH): λ[nm] (log ε) 376 (5.42), 528 (5.08, 708(4.89);

LR-MS (+FAB, 3-NBA) m/e (%): 682 (100, M⁺), 665 (31.1, M⁺ -OH) , 648(5.8, M⁺ -2OH), 613 (6.4, M⁺ -4OH -H);

HR-MS (+FAB, 3-NBA) calc'd for C₄₄ H₃₄ N₄ O₄ : 682.258??, found682.25470.

Z-isomer:

R_(F) =0.30 (silica gel, CH₂ Cl₂ /5.0% MeOH);

¹ H NMR (400 MHz, DMSO-d₆): δ=-1.75 (s, 2H, NH); 5.05 (br s, 4H, OH);5.95 (s, 4H, pyrrolidine-H); 7.65 (br s, 12H, phenyl-p,-m-H); 7.93 (brs, 4H, β-H); 8.09 (s, 8H, phenyl-o-H);

UV-Vis (CH₂ Cl₂ -0.5% MeOH): λ[nm] (log ε) 376 (5.42), 528 (5.08), 708(4.89);

LR-MS (+FAB, 3-NBA) m/e (%): 682 (19.4, M⁺); 665 (7.4, M⁺ -OH); 649(9.4); 648 (7.5, M⁺ -2OH); 613 (1.5, M⁺ -40H -H).

HR-MS (+FAB, 3-NBA) calc'd for C₄₄ H₃₄ N₄ O₄ : 682.25797, found:682.25518;

Example 6: Pinacol-Type Rearrangement to Form β-oxo-tetraphenylporphyrin(Cpd. 3) and B-oxo-tetraphenylmetalloporphyrin (Zn-3) ##STR32## Cpd. 3:2,oxy-5,10,15,20-tetraphenylporphyrin

100 mg (1.54×10⁻⁴ mol) of the starting material,3,4-dihydroxy-5,10,15,20-tetraphenylchlorin (Cpd. 2), were dissolved in10 ml CH₂ Cl₂, and 3 drops of HClO₄ (70% aqueous solution) were added.The mixture was refluxed for three minutes. Completion of the reactionwas indicated by a sharp peak at 520 nm in the UV-visible spectrum of analiquot neutralized with Et₃ N after about three minutes. The resultingbright green mixture was cooled, washed with aqueous NH₃, dried overanhydrous Na₂ SO₄, evaporated to dryness, and chromatographed on silica(10 g, 280-400 mesh) with CH₂ Cl₂ as an eluent. The product, Cpd. 3, wascrystallized from CH₂ Cl₂ /hexane. Yield: 92 mg (95%).

Alternatively, the zinc chlorin Zn-2 was used as a starting compound.Under the dehydration conditions (refluxing CHCl₃ with a drop ofconcentrated HClO₄), the product was demetallated, yielding Cpd. 3. Lessacid-labile complexes of Cpd. 2, like Ni-2 or Cu-2, were dehydratedunder these conditions without concomitant demetallation. Under lessharsh conditions (CHCl₃ containing a drop of concentrated HCl at roomtemperature), Zn-2 was demetallated without dehydration.

Zn-3: (2-oxy-5,10,15,20-tetraphenyl-porphyrinato) zinc(II)

Cpd. 3 was metallated with Zn(II)-acetate in pyridine/CHCl₃ to formZn-3.

The β-oxoporphyrin, Cpd. 3, and the β-oxometalloporphyrin, Zn-3, provedto be identical with the compounds described by Crossley, et al. J. Org.Chem. 53:1132-37 (1988).

Example 7: Isopropylidene Acetal ##STR33##

20 mg of [2,3-vic-dihydroxy-tetraphenylporphyrinato]Zn(II) were refluxedfor 20 minutes in 10 ml of dry acetone with 100 mg of freshly fusedZnCl₂. Evaporation to dryness and column chromatography (silica gel/CH₂Cl₂) yielded 12.5 mg (60%)[(2,3-di-O-isopropylidene)-5,10,15,20-tetraphenylchlorinato]zinc(II).

¹ H NMR (300 MHz, CDCl₃) δ=0.61 (s, 3H, CH₃ -a); 1.37 (s, 3H, CH₃ -b);6.46 (s, 2H, pyrroline-H); 7.55-7.76 (m, 12H, phenylA,B-(m,p)-H); 8.05(dd, J=8.0, 2.1Hz, 4H, phenyl-o); 8.12 (hidden m, 4H, phenyl-o); 8.16(d, J=6.0Hz, 4H, β"-H); 8.41 (s, 2H, β-H); 8.53 (d, J=6.0Hz, 2H, β'-H);

UV-Vis (CH₂ Cl₂): λ=418 (Soret), 520, 564, 594 (sh), 612 nm;

LR-MS (+FAB, 3-NBA) m/e(%)=750 (11,M⁺); 693 (23,M⁺ -C3H6O);

HR-MS (+FAB, 3-NBA)) m/e calc'd for C₄₇ H₃₄ N₄ O₂ Zn: 750.19732, found750.19422.

We claim:
 1. A β,β'-dihydroxy meso-substituted chlorin, bacteriochlorinor isobacteriochlorin compound having the formula (I) or (II): ##STR34##wherein M is a metal selected from the group consisting of Ni(II),Cu(II), Zn, Sn, Ge, Si, Ga, Al, Mn(III), Gd(III), In and Tc;A is a ringhaving the structure: ##STR35## D is a ring having the structure:##STR36## R₁ through R₆ are independently a hydrogen atom, a lower alkylgroup, a lower alkyl carboxylic acid or acid ester group, keto, hydroxy,nitro, amino, or a group that, taken together with another ring, ringsubstituent or meso-substituent, forms a fused 5- or 6-membered ring;and S¹ through S⁴ are H, substituted or unsubstituted alkyl groups,substituted or unsubstituted cycloalkyl groups, or substituted orunsubstituted aromatic rings, which may be the same or different, withthe proviso that at least one of S¹ through S⁴ is not H.
 2. The compoundof claim 1 having the formula (I) wherein M is Zn.
 3. The compound ofclaim 1 having the formula (II).
 4. The compound of claim 1 wherein atleast one of A and D is a ring having the structure: ##STR37##
 5. Thecompound of claim 1 wherein R₁ through R₆ are independently hydrogen,methyl, ethyl, or lower alkyl esters.
 6. The compound of claim 1 whereinS¹ through S⁴ are selected from the group consisting of phenyl,naphthyl, pyridinyl, and lower N-alkyl pyridinium salts.
 7. The compoundof claim 1 wherein at least one of S¹ through S⁴ has the structure:##STR38## wherein X, X', Y, Y' and Z are independently hydrogen,halogen, lower alkyl, lower alkoxy, hydroxy, carboxylic acid or acidsalt, carboxylic acid ester, sulfonic acid or acid salt, sulfonic acidester, substituted or unsubstituted amino, cyano, nitro, or abiologically active group, and Z' is hydrogen or lower alkyl.
 8. Thecompound of claim 7 wherein X, X', Y, Y' and Z are selected from thegroup consisting of hydrogen, methyl, ethyl, t-butyl, methoxy, hydroxy,and OR, where R is an alkyl group or a fatty acid group having from 6 to18 carbon atoms, fluoro, chloro, iodo, bromo, --C(O)-OCH₃, cyano ornitro.
 9. The compound of claim 7 wherein X, X', Y and Y' are eachhydrogen and Z is selected form the group consisting of hydrogen,halogen, lower alkyl, lower alkoxy, hydroxy, carboxylic acid or acidsalt, carboxylic acid ester, sulfonic acid ester, sulfonic acid or acidsalt, nitro, amino and cyano.
 10. The compound of claim 7 wherein atleast one of X, X', Y, Y' and Z is a substituent that increases theamphiphilic nature of the molecule.
 11. The compound of claim 1 whereineach of S¹ through S⁴ is selected from the group consisting of phenyl,pyridinyl, and lower N-alkyl pyridinium salts.
 12. The compound of claim11 wherein S¹ through S⁴ are identical.